Conventionally, in image forming apparatus, a photosensitive drum as an image carrier is charged by a charging roller as a charging member, an electrostatic latent image is written, with an LED as an exposure member, to the charged photosensitive drum, and the electrostatic latent image part is developed with toner by a development roller as a developer carrier. However, there is configuration in which, by a pair of supply rollers as developer supply members that are in contact with the development roller, toner is supplied to the development roller and, further, undeveloped toner on the development roller is scraped off (for example, Japanese Patent Laid-Open Publication No. HEI 10-39628 (page 4, FIG. 1)).
The toner in a toner container is supplied from a top central portion and sequentially moves toward two end portions. Further, since a commonly image-formed pattern is mostly in the central portion, toner consumption amount due to printing is larger at the central portion than at the two end portions. Therefore, in the conventional apparatus, there is a problem that, along with printing, fresh toner tends to be sequentially supplied and consumed at the central portion. On the other hand, old toner tends to remain at the two end portions as being pushed and is likely to agglomerate; the agglomerated toner clogs between the development roller and a development blade so that vertical streaks are likely to occur on a print image.
A development device disclosed in the application includes a developer container that contains developer; a rotatable electrostatic latent image carrier that forms an electrostatic latent image thereon, being arranged below the developer container; a rotatable developer carrier that provides the developer to the electrostatic latent image carrier so that the electrostatic latent image is developed with the developer to form a developer image; and rotatable first and second developer supply members that supply the developer to the developer carrier. Wherein the first developer supply member and the second developer supply member are arranged next to each other and facing the developer carrier, and an outer diameter (D12) of a central portion of the first developer supply member in a rotation axis direction is smaller than outer diameters (D11, D13) of two end portions of the first developer supply member.
According to the present invention, a flow path of the developer is formed over the entire developer container so that aggregation of the developer that is likely to occur at the end portions in the container is suppressed and thus occurrence of vertical streaks on a print image can be suppressed.